In the ink-jet printing apparatus, dots are formed in desired positions of the printing paper by ejecting the ink from the nozzle by virtue of the pressure generated by the distortion of the piezoelectric element or the pressure generated by the bubble, and thus characters, figures, etc. are printed on the printing paper.
Meanwhile, in order to improve the resolution of the printed image, recently finer dots are formed by reducing an amount of ink droplets ejected from the nozzle in one ejection operation.
The ejection of the ink is liable to be affected by the static electricity generated by the friction between members in the printing apparatus whenever an amount of ink is reduced in this way. Therefore, a method of providing a static electricity eliminating unit was proposed.
In this case, the ink droplets sometimes stall in the middle of the flight toward the printing paper when an amount of ink is reduced, and thus micro ink droplets floating in the air are generated.
In case the printing paper is charged with the static electricity in the situation in which such micro ink droplets are present, such micro ink droplets are adsorbed by the printing paper to form the dots on unintended portions, and thus in some cases the smudge is generated on the image.
Also, in recent years the printing apparatus having a function of printing the image on the overall area of the printing paper, i.e., a so-called “unframed printing” function is provided. In such printing apparatus, the blank is prevented from being generated by setting a size of the to-be-printed image slightly larger than a size of the printing paper.
In case the size of the image is set somewhat larger than the size of the printing paper in this manner, the ink droplets ejected toward portions that are in excess of the size of the printing paper fly to the ink absorbing material located behind the printing paper, and then are absorbed there.
However, the probability of the ink droplets stalling is enhanced since a distance to the ink absorbing material is longer than a distance to the printing paper. As a result, such a problem exists that the smudge of the printing paper is prone to occur.
Also, in the unframed printing, in order to prevent the event that the omission of the ink distribution occurs in the upper end portion of the printing paper and thus the concerned portion remains still white, sometimes the printing in predetermined color ink on the upper end of the printing paper, i.e., the so-called “waste printing” is carried out before the printing is started after the paper is fed.
In such waste printing, the ink is ejected onto the upper end of the printing paper to draw a streak of fine line. Thus, such problems arise that the ink emitted from the nozzles corresponding to portions except the concerned “line” becomes the foregoing micro ink droplets and that such ink droplets stick to the back surface of the printing paper, for example, to smudge the printing paper.
Also, the case where the ink droplets are ejected toward locations other than the printing paper due to the precision of the printing-paper feeding mechanism occurs except for the waste printing.
In such case, such a problem also exists that the smudge of the printing paper is caused, like the above case.
The subject that the present invention intends to overcome has been made in view of above circumstances, and it is an object of the present invention to provide a printing apparatus and a printing method, capable of preventing a backing of a printing paper from being smudged with a micro ink droplet.